(1) Field of the Invention
This invention relates generally to positioning of x-y tables and relates more specifically to transfer electrical energy to a movable part of the x-y table via rolling elements of rolling-element bearings guiding the x-y table.
(2) Description of the Prior Art
A precise positioning of x-y tables can be very difficult if signals or electrical power have to be brought forward or received from/to a moving x-y table. In prior art often a flexible cable is used for this purpose. The disadvantage of using a flexible cable for this purpose is that this kind of cable can act like a spring and impose an undesired force to the moving x-y table and hence a wrong or a slow positioning will occur. In case of e.g. a camera module having a lens barrel mounted on an x-y table that is guided by low friction ball bearings a fast and precise positioning has to be performed to accommodate the lens barrel to unintentional movements of the camera.
It is a challenge for the designers of small x-y tables to achieve a fast and precise positioning if ball bearings are used to guide the movements of the x-y table, if electrical energy has to be brought to/from the moving part of an x-y table.
Solutions dealing with ball bearings and electrical transmission are described in the following patents:
U.S. Patent (U.S. Pat. No. 7,109,610 to Tamai) teaches a wireless linear motor comprising: a stationary stator having permanent magnets; a movable stage having coils and a controller with a transceiver for wirelessly communicating with an external data processing system, the controller adapted to energize the coils to position the stage over the stator in response to control signals from the external system; and, a frame having first and second electrically conductive linear guides for slideably mounting the stage over the stator, wherein each linear guide has a stage portion attached to the stage through a first electrical insulator, a frame portion attached to the frame through a second electrical insulator, a plurality of ball bearings disposed between and electrically coupling the stage and frame portions, and a conductor coupling the stage portion to the controller for providing electrical power from an external power supply to the controller through the frame portion of each guide.
U.S. Patent (U.S. Pat. No. 7,043,146 to Semaza) discloses an all season fan with heated circulating blades includes heating elements mounted in slots defined in the rear surface of the fan blades for heating of air blown outwardly therefrom. Resilient biasing devices such as a bow springs are mounted in the fan blades extending over the slots to retain the heating elements in the slots.
U.S. Patent (U.S. Pat. No. 6,180,901 to Bauer et al.) discloses an electrical rotary switch for several switch positions having a control knob mounted in a housing supported on first, second and third ball bearings that, guided by a cage disk, roll in a housing groove formed by an axial wall and a radial wall against which the ball bearings are loaded under an applied force of a conical bearing surface of the control knob. Axial and radial wall bearing surfaces respectively have first and second contact segments and first, second and third contact bands thereon that extend out of the housing via terminal lugs, the first contact segment and first contact band being shorted by the first ball bearing in predetermined switch positions. In a last switch position, contact occurs between the second contact segment and the second and third contact.